Antenna matching device

ABSTRACT

A radio including an antenna and an impedance-matching network for adjusting the impedance of the radio to match the impedance of the antenna over a range of operating frequencies. The antenna includes a radiating arm, a base portion and a cam surface attached to the base portion for indicating the impedance of the antenna over the range of operating frequencies. The impedance matching network is adjusted by a pair of cam followers which mate with the cam surface. A frequency tuning knob is connected by a threaded arm to the cam followers for moving the cam followers over the cam surface while the radio is being tuned by rotating the knob.

United States Patent [72] Inventor Dieter R. Lohrmann Eatontown, NJ. [21] Appl. No. 868.238 22 Filed oa.21, 1969 [45] Patented July 20, 1971 [73] Assignee The United States 01 America as represented by the Secretary of the Army [54] ANTENNA MATCHING DEVICE 3 Claims, 1- Drawing Fig.

[52] US. Cl 325/160, 325/171, 325/172, 325/178, 325/452, 325/457, 334/62 [51] Int. Cl H0411 1/00 [501 Field otSearch 74/106, 10.85, 89, 89.14, 89.15; 325/124, 160, 171173, 178, 452, 457; 334/61, 62, 72, 78, 80

[56] References Cited UNITED STATES PATENTS 1,577,613 3/1926 Dunmore 334/62 1,882,684 10/1932 Achard 2,551,756 5/1951 Mittelmann ABSTRACT: A radio including an antenna and an impedancematching network for adjusting the impedance of the radio to match the impedance of the antenna over a range of operating frequencies. The antenna includes a radiating arm, a base portion and a cam surface attached to the base portion for indicating the impedance of the antenna over the range of operating frequencies. The impedance matching network is adjusted by a pair of cam followers which mate with the cam surface. A frequency tuning knob is connected by a threaded arm to the cam followers for moving the cam followers over the cam surface while the radio is being tuned by rotating the knob.

ANTENNA MATCHING DEVICE This is a continuation of application Ser. No. 574,510, filed Aug. 22, 1966 now abandoned.

The present invention relates to an antenna-matching device.

ln the field of high-frequency radio communications, it has been the general practice to employ antenna-matching networks which usually include a means for electrically detecting the amount of mismatch between the antenna and the radio set, and a means for automatically varying a potentiometer or other variable impedance until the mismatch is zero. Such devices besides being expensive have an added disadvantage in that a relatively strong signal must be generated in the an tenna in order to electrically detect the impedance of the antenna at a particular frequency. Signals generated in the antenna as a result of receiving a transmitted signal from a distant radio would not usually be of a sufficient strength to permit detection of the impedance thereof. Therefore, in order to provide automatic matching by detecting electrically the antenna impedance, it is usually necessary to transmit energy from the radio at the'frequency in question. If the radio is used mainly as a receiver, this requirement can become expensive, since some sort of transmitting means must be provided. There are also occasions when security is important and transmission of energy, to provide automatic matching, may be undesirable since the transmission may be used by an enemy force, for example, to detect ones position. Therefore, those concerned with the development of such radios have long recognized the need for an efficient antenna-matching device which does not require the transmission of energy from the antenna. One of the most critical problems confronting the designers of such devices has been the developing of a matching device which would also permit the interchange of different antenna with a given radio.

Therefore, an object of the present invention is the provision of an automatic antenna-matching system which does not require transmission from the antenna.

- Another object is to provide an automatic antennamatching device which will be compatible with any one of a plurality of antennas having different impedance characteristics.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description and the annexed drawing which shows a perspective view partly schematic of a preferred embodiment of the invention.

There is shown in the drawing a radio set 11 having an antenna 12 mounted on the exterior ofa housing 13. Antenna 12 includes an antenna arm 14 held by an insulated base portion 15. Joined to base 15 is a cam 16 having two camming surfaces l7 and 18. Cam 16 may be stamped from a piece of sheet metal or the like and then simply secured to base 15 such that cam 16 protrudes into housing 15 and into engage- .ment with a pair of cam followers 19 and 20.

Cam followers 19 and 20 are formed from rigid rods having 1 bent end portions 21 and 22 respectively for engagement with camming surfaces 17 and 18 respectively. Followers 19 and 20 are slidably mounted on a block 23 and are biased into engagement with surfaces 17 and 18 respectively by springs 24 and 25 which are compressed between block 23 and flanges 26 and 27 on followers 19 and 20 respectively. Stop flanges 28 and 29 are provided on followers 19 and 20 to limit the axial motion thereof. A pair of variable impedance devices 30 and 31 of an antenna-matching network 34 are mounted on followers 19 and 20. Antenna 12 is connected to network 34 by conductor 43. The variable impedance devices 30 and 31 may be any of the well-known devices for use in a network 34 which adjusts respectively the real and imaginary parts of the antenna input impedance of set 11. They could also be potentiometers the positioning and hence output voltage of which tells a motor drive where to position the actual impedancematching elements (like variable coils, variable capacitors, capacity diodes or the like). A pair ofguides 32 and 33 engage devices 30 and 31 to prevent motion of the devices 30 and 31 in the axial direction of followers 19 and 20. However, devices 30 and 31 are free to slide vertically between guides 32 and 33 when block 23 is moved vertically. Followers 19 and 20 will move axially and vertically under the influence of block 23 and camming surfaces 17 and 18. The real and imaginary parts of the antenna input impedance of set 11 will therefore vary as followers 19 and 20 move axially.

Block 23 is threaded on shaft 36 for movement along the shaft 36. Shaft 36 is an extension of the frequency tuning shaft 37 which extends to the exterior of housing 13 where a frequency-tuning knob 38 is mounted thereon. A frequency tuner element 40 is controlled by shaft 37. Frequency tuner 40 may be any of the well-known variable capacitors or inductors made for this purpose. Box 41 represents the remaining components ofa typical radio set. The frequency tuner 40 and the network 34 are connected to the components in the usual manner by conductors 42 and 43 respectively. The impedance of a whip antenna is substantially dependent on frequency. Therefore, as the operating frequency of the radio set 11 is changed by turning the knob 38, the impedance of antenna 12 changes. In order to maintain an impedance match between the antenna 12 and the other components of radio set 11, the impedance of set 11 must also be varied. As knob 38 is turned to operate the frequency tuner 40, the impedance tuner or variable impedance devices 30 and 31, which are designed to adjust the real and imaginary parts of the radio antenna input impedance, are varied to provide the proper phase and amplitude values required to maintain a match. The actual values that the devices 30 and 31 are tuned to will depend on the shape of camming surfaces 17 and 18. The shape of these camming surfaces may be determined when the antenna is manufactured. The cam 16 may then be cut or stamped from a piece of sheet metal and fastened to base 15. The cam 16 will have a specific predetermined shape for each antenna type and will therefore remain as an integral part ofthe antenna assembly.

It should be understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and scope of the invention as set forth in the appended claims.

What I claim is:

l. A radio comprising an antenna means having a base portion for mounting a radiating arm portion; a frequency tuning means having a manual adjusting means for tuning said radio over a range of operating frequencies; a variable impedance matching means for matching the impedance of said radio to the impedance of said radiating arm portion over said range of operating frequencies; a keying means secured to said base portion and having a camming surface means having a shape which is a function of the impedance of said radiating arm portion over said range of operating frequencies; a control means having a cam follower means for slidably engaging said camming surface means and connected to said variable impedance means for varying the impedance thereof; and means responsive to said manual adjusting means and connected to said control means for sliding said cam follower means over said camming surface means upon adjustment of said frequency tuning means.

2. A radio comprising an antenna having a radiating arm portion and a base portion for mounting said arm portion; a cam surface means rigidly secured to said base portion and removable therewith; a frequency-tuning means, having a threaded shaft extending therefrom, for tuning said radio over a range of frequencies and for simultaneously rotating said threaded shaft; mounting means threaded on said shaft for linear movement along said shaft upon rotation thereof; a cam follower means slidably mounted on said mounting means and biased into slidable contact with said cam surface means; and an impedance matching means connected to said cam fol- 3 1 lower means for varying the impedance of said radio upon slidable movement of said cam follower means by said cam surface means.

3. The device according to Claim 2 and wherein said cam mounted in sliding contact with a different one of said cam sections; said cam followers each connected to said impedance-matching means for adjusting'respectively the real I and ima inar arts ofthe im edance ofsaid radio. surface means comprises two sections and said cam follower 5 g y p p 1 means comprises two cam followers; each said follower 

1. A radio comprising an antenna means having a base portion for mounting a radiating arm portion; a frequency tuning means having a manual adjusting means for tuning said radio over a range of operating frequencies; a variable impedance matching means for matching the impedance of said radio to the impedance of said radiating arm portion over said range of operating frequencies; a keying means secured to said base portion and having a camming surface means having a shape which is a function of the impedance of said radiating arm portion over said range of operating frequencies; a control means having a cam follower means for slidably engaging said camming surface means and connected to said variable impedance means for varying the impedance thereof; and means responsive to said manual adjusting means and connected to said control means for sliding said cam follower means over said camming surface means upon adjustment of said frequency tuning means.
 2. A radio comprising an antenna having a radiating arm portion and a base portion for mounting said arm portion; a cam surface means rigidly secured to said base portion and removable therewith; a frequency-tuning means, having a threaded shaft extending therefrom, for tuning said radio over a range of frequencies and for simultaneously rotating said threaded shaft; mounting means threaded on said shaft for linear movement along said shaft upon rotation thereof; a cam follower means slidably mounted on said mounting means and biased into slidable contact with said cam surface means; and an impedance matching means connected to said cam follower means for varying the impedance of said radio upon slidable movement of said cam follower means by said cam surface means.
 3. The device according to Claim 2 and wherein said cam surface means comprises two sections and said cam follower means comprises two cam followers; each said follower mounted in sliding contact with a different one of said cam sections; said cam followers each connected to said impedance-matching means for adjusting respectively the real and imaginary parts of the impedance of said radio. 